The world is talking about an Ethiopian Airlines crash on Sunday that killed all 157 people onboard, despite little being known about how a fairly quotidian commercial flight on a new plane, with a highly rated African airline, could have such fatal problems six minutes after takeoff on a clear day. Local and international safety agencies, including the U.S. Federal Aviation Administration and National Transportation Safety Board, are investigating, but while they await recordings from the recovered black boxes, several countries have preemptively grounded the type of plane that crashed on Sunday: a Boeing 737 Max 8.

This is the second time in less than six months a Boeing 737 Max 8—a 2017 update to the most popular regional jet of all time, the 737—has suffered a deadly crash. (Back in October an Indonesian flight, Lion Air Flight 610, went down within minutes of takeoff, killing all 189 onboard.) Readers and frequent fliers alike have a lot of questions about this Boeing plane making headlines, so we contacted our aviation sources to discuss some of the biggest, and most pressing. We'll continue to update this story as we learn more.

How many U.S. airlines fly the 737 Max 8?

Just two, according to the FAA and Boeing. Southwest has the largest number of any domestic carrier, 34 (and orders for 219 more), while American Airlines has 24 of the jets. United and Delta—two of America's "Big Three" airlines—do not currently have any Max 8s in their fleet.

What are my chances of flying a 737 Max 8 somewhere?

By our latest count, there are about 350 of these jets being used around the world, owned by 54 airlines, including Air Canada (with 24 planes), Norwegian (with 18 planes), WestJet (13), and Icelandair (3). China's "Big Three"—China Airlines, China Eastern, and China Southern—had one of the largest and most recent orders, buying 97 Max 8s, according to CNN.

Where are the 737 Max 8 planes being grounded?

As of Tuesday, March 12, "Britain, Australia, Singapore, Malaysia, and Oman banned all Boeing 737 Max 8 planes from their airspaces," according to The New York Times; Egypt, Ethiopia, China, France, Ireland, Germany, India, and Indonesia have also grounded the Max 8—and as of Wednesday, March 13 Canada's Minister of Transport Marc Garneau announced that as the result of new data received, 737 Max 8 and 9 aircraft will not be allowed to take off, land or fly over Canadian airspace, according to CBC News The same applies in Hong Kong. China's Civil Aviation Administration cited "zero tolerance for safety hazards." Meanwhile, the Civil Aviation Authority of Singapore said it was "temporarily suspending operation of all variants of the Boeing 737 MAX aircraft into and out of Singapore in light of two fatal accidents involving Boeing 737 MAX aircraft in less than five months." Singapore's Changi Airport is one of the busiest in Asia; the city-state's regional carrier SilkAir owns and operates six Max 8 planes.

Are flights being canceled?

Norwegian just canceled its Dublin to Providence, Rhode Island and Dublin to New York–Stewart flights. (Both were about to take off.) Return flights tonight are also canceled. Icelandair's B38M from New York-JFK departed last night for Reykjavik; its flight back, today, has been replaced by an older 767 aircraft.

Are groundings of an aircraft type common?

Not particularly. “I think it's safe to say that governments grounding fleets of a particular aircraft is pretty rare,” says Frank Jackman, spokesman of the Alexandria, Virginia-based Flight Safety Foundation. He recalled two of the most notable incidents: When the U.S. Federal Aviation Administration (FAA) grounded the Boeing 787 in early 2013 due to battery issues, and the grounding of the DC-10 fleet in 1979 following an American Airlines crash at Chicago O’Hare.

What are the U.S. airlines and authorities saying?

Domestic airlines and the FAA all stand by Boeing. The FAA "said in its advisory Monday that it had not been provided with any information that would draw similarities between the incidents in Indonesia and Ethiopia," reports the Chicago Tribune. "We remain confident in the safety and airworthiness of our fleet of more than 750 Boeing aircraft," Southwest Airlines said in a statement Monday. American Airlines added in a statement: "At this time there are no facts on the cause of the accident other than news reports. ... We have full confidence in the aircraft and our crew members, who are the best and most experienced in the industry."

What's Boeing saying?

Boeing issued two statements in the past 24 hours—one announcing its commitment to completing a software enhancement on the Max 8, mandated by the FAA, and one reiterating that "safety is Boeing's number one priority."

March 11 statement, excerpted: "For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer. This includes updates to the Maneuvering Characteristics Augmentation System (MCAS) flight control law, pilot displays, operation manuals, and crew training. The enhanced flight control law incorporates angle of attack (AOA) inputs, limits stabilizer trim commands in response to an erroneous angle of attack reading, and provides a limit to the stabilizer command in order to retain elevator authority. ... The FAA says it anticipates mandating this software enhancement with an Airworthiness Directive (AD) no later than April. We have worked with the FAA in development of this software enhancement."

March 12 statement: "Safety is Boeing’s number one priority and we have full confidence in the safety of the 737 MAX. We understand that regulatory agencies and customers have made decisions that they believe are most appropriate for their home markets. We’ll continue to engage with them to ensure they have the information needed to have confidence in operating their fleets. The United States Federal Aviation Administration is not mandating any further action at this time, and based on the information currently available, we do not have any basis to issue new guidance to operators."

What is the difference between a 737-800 and a 737 Max 8?

The 737 Max 8 is a newer version of the 737 than the -800 model, with the most notable change being that it uses a different engine type. They’re both based on the same concept—the 737 has always had a single aisle and been smaller than models such as the 777 and 747—but new aircraft versions still need to go through a certification process before they can fly. The 737 Max 8 took its first flight in January 2016, and belongs to the latest 737 family. You can think of a family as the latest generation of the aircraft type, and within that group are specific models with varying lengths and seating capacity. So, the “Max” part of the name relates to the family, and the 8 refers to how the aircraft’s dimensions compare with the shorter Max 7 or longer Max 9. The 737-800 version, on the other hand, is part of the previous “next-generation” family of 737s that debuted in the late 1990s. That group also includes the 737-700 and -900, which are still commonly-used among the world’s airlines. Before that are the oldest 737s, which are sometimes called the “classics” and include the -300s, -400s and -500 models. We rarely see those aircraft flying commercially because of their age.

What are the similarities between the Ethiopian Airlines crash and the Lion Air crash?

In both instances, the commercial jets—en route on short, regional flights—reported problems not long after takeoff, within six to 12 minutes. Both pilots requested to return to base. As we await details on Ethiopian Airlines, an 2018 investigation into the Lion Air crash showed that "pilots struggled to keep the nose of their Boeing 737 Max 8 plane up, as faulty sensor readings kept dipping the plane's nose down over the course of their 11-minute flight, according to a preliminary report by Indonesia’s National Transportation Safety Committee (NTSC)," we previously reported. "The flight data recorder—known as the black box—showed that the pilots tried to right the plane some two-dozen times, fighting 'a computerized system Boeing installed on its latest generation of 737 to prevent the plane’s nose from getting too high and causing a stall,' per The New York Times."

How often do new airplanes have problems?

As Barbara Peterson reported in November, "even before a new airplane model carries its first paying customer, it undergoes years of rigorous tests under extreme conditions. A typical plane is composed of thousands of parts involving hundreds of different outside vendors."

"Even so, it’s not unheard of for new plane types to experience glitches early in their life spans, although they rarely lead to fatal crashes. Take the case of the Boeing 787 Dreamliner, which the FAA grounded in 2013—in its first year of service—following a string of incidents in which the plane’s lithium batteries caught fire. The action affected more than 100 flights a day and not only had a serious impact on international travel, but called into question the safety of the plane itself. The batteries were found to be prone to overheating; the planes were returned to service after Boeing designed a new system to encase the batteries to better contain fire and smoke."

I checked my flight for this weekend because, to be honest, I'm spooked. When will we have more details?

A spokesperson for Ethiopian Airlines has said, "It will take five days to clear everything" and the airline would release more details later Tuesday. In the meantime, you can check the type of plane you're flying on FlightAware—you just need the flight number.

What if I don't want to be on a Max 8? Can I change my flight?

Yes, you can always change your flight, but you'll have to pay any corresponding fees that your airline charges—airlines aren't currently issuing waivers for these changes like they might during, say, a bad storm. "The important thing to remember is that accidents like this are extremely rare: Data showed that one fatal accident occurred for every 16 million flights in 2017," wrote Peterson.

This story is developing and will continue to be updated as we learn more. With reporting by David Jefferys and Kristin Majcher.